The present invention relates to brake apparatus, air actuated, as used in large vehicles including, e.g., trucks, trailers, buses, tractors, and some larger recreational vehicles.
More particularly, the present invention relates to the brake adjustment apparatus which is an integral part of the braking mechanism, as exists between the air chamber cylinder of the brake apparatus and the brake drum and the brake shoe whose forceful engagement achieves the desired stopping effect of the vehicle.
For decades it has been known that air brakes inherently become out of adjustment, because of wear, looseness, and other factors; and the out-of-adjustment condition presents a danger to the driver and the public, as well as of course to the vehicle.
The problem is compounded by the fact that larger vehicles have a plurality of brake mechanisms (because of the plurality of wheels), and when the brake mechanisms of the plurality of brake systems come into conditions of differing adjustment, the situation becomes not merely that of poor vehicle-stopping effect, and brake wear, but also of poor vehicle control due to the braking effect being different at different portions of the overall vehicle.
A further and long known problem of air-brake adjustment is that drivers, mechanics and other maintenance people will over-adjust the air brakes in order to compensate for the movement and keep the brakes in adjustment for a longer period of time. This over-adjustment results in excessive brake wear, which in itself is expensive and eventually dangerous.
In order to adjust the brakes with or without automatic slack adjusters, a person has had to crawl under the vehicle, mark the brake rod, come out from under and apply the brakes from the cab, then get back under and measure the distance the mark has moved, a procedure that discourages proper maintenance.
Automatic slack adjusters were introduced to adjust the brakes automatically when they became out of adjustment. This does partially solve the problem; however, they are not entirely accurate, and become dirty, and being mechanical are subject to wear. They often are improperly installed. Many will over-adjust when brakes get out of adjustment, resulting in premature brake wear.
To confront the out-of-adjustment situation, automatic slack adjusters, along with visual brake stroke indicators to show if brakes are being properly adjusted, are being used and are becoming mandatory; and the present invention and its concepts advantageously provide brakes-adjustment indication both with and without the use of automatic slack adjusters, and will provide a determination of brake rod adjustment within both minimum and maximum limits.
As shown herein, the prior art has attempted, with varying amounts of success, brake adjuster indicator mechanisms; and such prior art has shown a long recognization of problems of brake stroke indicators, such as (a) a desirability of relatively easy visibility of the indicator without having to get under the vehicle; (b) the indication of brake adjustment as being under-adjusted, over-adjusted, or within legal limits; (c) preferably indicate how much travel remains before exceeding the legal limits; (d) allow a visual inspection to determine if all brakes were displaying balanced braking action; and (e) help indicate proper brake balance when brakes are replaced: etc.; and by novel means and novel concepts, the present invention achieves all of those criteria, advantageously, and with a novel cooperation of components,. and also provides other advantages as explained herein.